Studies of estrogen receptor structure using molecular dynamics

在原代培养的未成熟雄性虹鳟鱼(RT)肝细胞中，卵黄蛋白原(VG)基因的表达受雌激素受体(ER)调节。然而，雌激素以外的类固醇也可以刺激VG基因的表达。这些类固醇在孵育过程中几乎不会转化为E2，它们的刺激活性可被三苯氧胺完全抑制，这意味着它参与了雌激素受体的作用。这些类固醇在康诺利表面不带电荷或略带正电荷。相反，由于极化，未能刺激VG基因表达的类固醇在C和D环周围有很强的正电荷或负电荷。Rter与人Era的配体结合区(LBD)的氨基酸序列有57.7%的同源性，推测的类固醇结合部位只有一个氨基酸不同。我们利用HERA的X射线结晶学数据模拟了RTER的LBD的三维结构，以研究类固醇和RTER之间的匹配(结构和静电)。与RTER结合的两个因素是：(I)类固醇C3和Di C17附近的羟基或羰基，它们可以与His(489)，Arg(359)和Glu(318)形成氢键，(Ii)通过van der Waals力与RTER LBD的疏水区域相互作用的疏水类固醇核。如果存在极性官能团，则类固醇与RTER LBD之间的疏水相互作用会大大减弱。

In primary cultures of immature male rainbow trout (rt) hepatocytes, vitellogenin (Vg) gene expression regulated by E2 via the estrogen receptor (ER). However, steroids other than estrogens can also stimulate Vg gene expression. These steroids are hardly converted into E2 during incubation and their stimulatory activity is completely inhibited by tamoxifen implying rtER involvement. These steroids have no or a slightly positive charge on the Connolly surface. In contrast, steroids that failed to stimulate Vg gene expression had a strong positive or negative charge around rings C and D due to polarization. The ammo acid sequences of the ligand binding domains (LBD) of rtER and human ERa have 57.7% homology; only one amino acid differs in the presumed steroid binding site. We modeled the three-dimensional structure of the LBD of rtER using X-ray crystallographic data for hERa in order to investigate the fit (structural and electrostatic) between steroid and rtER. Two factors are essential for binding to rtER: (i) hydroxyl or carbonyl groupsi near C3 andI C17 of the steroids (hydrophilic regions) that can form hydrogen bonds with His(489), Arg(359) and Glu(318), (ii) a hydrophobic steroid nucleus that interacts with a hydrophobic region of the rtER LBD through van der Waals forces. If polar functional groups are present, the hydrophobic interaction between steroid and the rtER LBD is considerably weakened.